Optical spectroscopy is the study of the interaction of light with matter. Typically, optical spectroscopy involves monitoring some property of light that is changed by its interaction with matter, and then using that change to characterize the components and properties of a molecular system. Recently, optical spectroscopy has been used in high-throughput screening procedures to identify candidate drug compounds.
Optical spectroscopy is a broad term that describes a number of methods, such as absorption, luminescence (such as photoluminescence and chemiluminescence), scattering/reflectance, circular dichroism, optical rotation, and optical microscopy/imaging, among others. In turn, each of these terms describes a number of more closely related methods; for example photoluminescence includes fluorescence intensity (FLINT), fluorescence polarization (FP), fluorescence resonance energy transfer (FRET), fluorescence lifetime (FLT), total internal reflection fluorescence (TIRF), fluorescence correlation spectroscopy (FCS), fluorescence recovery after photobleaching (FRAP), and their phosphorescence analogs, among others.
Unfortunately, optical detection systems for use in optical spectroscopy suffer from a number of shortcomings. In particular, optical detection systems generally involve alignment of a sample and portions of an optical relay structure (such as an optics head) for directing light to and from the sample. Such alignment may be accomplished by physically moving the sample relative to the optical relay structure, or by physically moving the optical relay structure relative to the sample. Typically, such movement is followed by a waiting period before measurement to permit vibrations to subside. Time spent during alignment and subsequent waiting periods is downtime because it is time during which data cannot be collected from the sample. Such downtime is especially significant in high-throughput screening, where tens or hundreds of thousands of samples must be aligned with an optical relay structure to conduct a particular study.
In principle, the number of alignment steps can be reduced by reading simultaneously from a plurality of samples or from a larger area of a single sample. However, simultaneous reading typically will reduce intensities, because excitation light is distributed to a larger area and because the distance between the sample and optical relay structure is increased. Reduced intensities may decrease signal-to-noise ratios, decreasing reliability, especially with less intense nonlaser light sources.